My invention relates to a method of manufacturing vehicle wheel rims from materials characterized by having a relatively low ductility such as aluminum, or high strength, low alloy (HSLA) steel. By my method, wheel rims of aluminum or HSLA steel may be manufactured using conventional mass production rim rolling apparatus presently used in the manufacture of SAE 1010 steel rims. Prior art roll forming techniques for forming wheel rims from sheet material have proven unsuccessful when applied to aluminum materials. Because of aluminum's lower ductility, sheet aluminum when roll formed on conventional rim rolling equipment resists the necessary stretching especially at the butt weld, to form an acceptable wheel rim section.
In the manufacture of steel wheel rims a strip of rolled sheet steel is coiled and butt welded to form a cylindrical hoop or band. After deburring the butt weld, the cylindrical band is first placed in a press wherein the lateral edges of the band are flared radially outward. Flaring of the edges serves to preform the rim flange area and provide a band cross-sectional profile suitable for retention on roll forming equipment used for subsequent forming operations. After flaring of the lateral edges the band is subjected to a series of roll forming operations whereby the band is progressively formed into the final desired cross-sectional profile and circumference. During roll forming and sizing operations, the band circumference expectantly increases. Thus the initial dimensions of the strip from which the band is formed are selected to accommodate such material elongation.
While the above described process has proven successful in the manufacture of SAE 1010 steel wheel rims it has not heretofore been successful for the manufacture of wheel rims from materials having a ductility significantly lower than that of SAE 1010 steel. Thus the prior art has been unsuccessful in roll forming aluminum sheet material into acceptable wheel rims. Because of aluminum's lower ductility bands of aluminum, having the dimensions as heretofore used in forming steel rims of a given wheel size, have not met the efficiency standards required for mass production. Because of aluminum's resistance to stretching (low ductility) the band lateral edges may not be flared to the same extent that a steel band is flared, without fracturing the butt weld. Increasing the band circumference to reduce the stress at the weld results in an oversize rim because of band growth during the roll forming operations.
Because of the aforementioned problems aluminum wheels heretofore have been produced by casting or forging techniques. However, cast or forged aluminum wheels are costly to manufacture and, because of the lower properties of cast aluminum or the processing requirement of forged aluminum, the wheels have such mass that no significant weight savings is realized. Therefore, it is preferable to use mill rolled aluminium sheet to take full advantage of the materials high strength, lower processing costs, and overall lower weight.